The debate continues over whether the degree of left ventricular outflow obstruction is an important discriminator of cardiac risk in patients with hypertrophic cardiomyopathy. Maron and colleagues conducted a prospective study of outflow obstruction in patients with hypertrophic cardiomyopathy and its association with death or heart failure.

The authors enrolled 1,101 consecutive patients diagnosed with hypertrophic cardiomyopathy at two cardiac referral centers in Italy and one in the United States. Echo-cardiographic measurement of the peak outflow gradient in the left ventricle was obtained under resting conditions, taking care to avoid any inclusion of the mitral regurgitation jet. Mean duration of follow-up was 6.3 years for risk of sudden death or progression to severe heart failure (New York Heart Association functional class III or IV).

At the time of last follow-up, 12 percent of the patient cohort had died as a result of hypertrophic cardiomyopathy, and 24 percent of the 914 surviving patients (216 patients) had progressed to severe heart failure. A peak outflow gradient of 30 mm Hg was considered the threshold at which the risk for death or heart failure progression increased, especially in patients older than 40 years (see accompanying figure). Outflow gradients higher than 30 mm Hg did not confer additional risk.

The authors concluded that echocardiographic measurement of a left ventricular outflow gradient greater than 30 mm Hg in patients with hypertrophic cardiomyopathy predicted an increased risk of death or severe heart failure, especially in patients older than 40 years.

editor’s note: The diagnosis of hypertrophic cardiomyopathy is relatively straightforward (i.e., hypertrophied left ventricular wall without chamber dilation). However, predicting the long-term outcome is not as clear-cut. The clinical course in the disease varies from incidental findings noted on echocardiography in asymptomatic patients to sudden death at a young age. While some previous studies had suggested that an outflow gradient greater than 50 mm Hg was a relative indication for intervention, other investigations noted that the degree of outflow obstruction did not seem to correlate with adverse outcomes. This larger study confirms a predictive role for quantifying outflow obstruction and sets a lower cutoff value for identifying patients at elevated risk for complications. The high rate of death and progression to severe heart failure over the relatively short time period in this study emphasizes the importance of stratifying risk and planning interventions in patients with hypertrophic cardiomyopathy.—b.z.